<!doctype html> 
<html> 
<head> 
    <meta charset="utf-8"> 
    <title></title> 
</head>
<script type="text/javascript">
	var a = '123';//new String('123');//new 
	var b = a;
	b.a = 10;
	alert(a.a)
</script>

<body>

<div id='sad' class='asda' lll='1'>
	
</div>
</body>
</html>